METHOD AND DEVICE FOR RECYCLING WASTE MATERIALS CONTAINING VALUABLE METALS

Abstract

The invention relates to processes for recycling waste materials containing valuable metals in a fluidized-bed furnace (100), comprising the phases I, start-up of the fluidized-bed furnace; and II, continuous reprocessing of the waste materials containing valuable metals, characterized in that the fluidized-bed furnace (100) is operated autothermally during the phase II of continuous reprocessing of the waste materials containing valuable metals, with the process temperature being regulated via the fill level of the fluidized-bed furnace (100) and the flow rate of material through the furnace. The invention further provides an apparatus comprising a fluidized-bed furnace (100) for recycling waste materials containing valuable metals in a continuous autothermal process.

Claims

1. Process for reprocessing waste materials containing valuable metals in a fluidized-bed furnace (100), comprising the phases: I. Start-up of the fluidized-bed furnace (100); and II. Continuous reprocessing of the waste materials, wherein the fluidized-bed furnace (100) is operated autothermally during the phase II of continuous reprocessing of the waste materials containing valuable metals, and reprocessing temperature in the fluidized-bed furnace (100) is regulated by the fill level in the fluidized-bed furnace (100) and the flow rate of material through the fluidized-bed furnace.

2. Process according to claim 1, characterized in that the temperature in the fluidized-bed furnace (100) during the continuous, autothermal phase II is kept in the range of 630° C. to 730° C.

3. Process according to claim 1 wherein the fluidized-bed furnace (100) is operated at a flow rate of material through the furnace of about 1000 kg/h during the continuous, autothermal phase II.

4. Process according to claim 1 wherein the fill level in the fluidized-bed furnace (100) in the continuous, autothermal phase II is kept in the range from 15% to 25%, controlled by a pressure differential measurement.

5. Process according to claim 1 wherein about 3000 to 5000 kg/h of process air, preheated to a temperature in the range from 45° C. to 130° C., is are introduced into the fluidized-bed furnace (100) during the continuous, autothermal phase II.

6. Process according to claim 1 wherein residence time of the waste materials containing valuable metals in the fluidized-bed furnace (100) during the continuous, autothermal phase II is about 4 hours.

7. Process according to claim 1 wherein the fluidized-bed furnace (100) is operated under reduced pressure, during the continuous, autothermal phase II.

8. Process according to claim 1 wherein the phase I start-up of the fluidized-bed furnace (100) comprises the steps: i) Introduction of previously reprocessed material into the fluidized-bed furnace while simultaneously blowing process air into the fluidized-bed furnace and fluidizing the material, ii) Heating of the fluidized-bed furnace to a reprocessing temperature using at least one gas burner, iii) Introduction of waste materials containing valuable metals, iv) Ignition of the reaction using an ignition burner, v) Switching-off of said at least one gas burner when the reprocessing temperature reaches 630° C. to 730° C.

9. Process according to claim 8 wherein the ignition burner is removed after completion of the phase I of start-up of the fluidized-bed furnace (100).

10. Apparatus for recycling waste materials containing valuable metals in a continuous autothermal process, comprising a fluidized-bed furnace (100) which comprises a steel vessel (108) having a refractory lining (118), an inlet (101) for waste materials containing valuable metals, at least one outlet for discharge of material (110, 111), and at least one inlet for introduction of process air (102), a preheating device for preheating the process air to a temperature in the range of 45° C. –130° C., at least one gas burner operated only for heating the fluidized-bed furnace (100) to temperature in the range of 720° C. to 730° C. during start-up, a fill level measuring device, preferably based on a differential pressure measurement between two measurement points (112, 113), of which one measurement point (113) is arranged above the bed of material and one measurement point (112) is arranged below the bed of material, at least one pressure meter (119) for measuring the pressure within the steel vessel (108), and at least one temperature sensor for measuring temperature in the fluidized-bed furnace (100).

11. Apparatus according to claim 10, characterized in that the at least one outlet (110, 111) for discharging material from the fluidized-bed furnace (100) has a flap for controlling the rate of discharge of material.

12. The apparatus according to claim 10 wherein the fluidized-bed furnace (100) further includes an air distributor (104) with air nozzles (105) for distributing the process air which is fed via the at least one inlet (102) into the fluidized-bed furnace (100).

13. The apparatus according to claim 10 characterized in that the fluidized-bed furnace (100) further includes an ignition burner (109) for one-off ignition/starting of the continuous, autothermal process phase II for recycling waste materials containing valuable metals.

14. The apparatus according to claim 10 further comprising a control device which is configured for controlling the fill level measuring device so that the fill level of the steel vessel (108) is kept in the range from 15% to 25% by means of the differential pressure measurement using the pressure sensors (112, 113) and taking into account the process temperatures of from 630° C. to 730° C., with the discharge of material being effected under gravity by control of the flap in the at least one outlet (110, 111); and/or keeping the process temperature in the range from 630° C. to 730° C., with the process air being preheated to a temperature in the range of 45° C. – 130° C. by means of the preheating device, and/or setting the pressure in the interior of the steel vessel to a value in the range from -0.2 to -0.3 mbar by control of an extraction device for the exhaust gases.

15. The apparatus according to claim 10 further comprising at least one auxiliary device selected from the group consisting of a differential metering balance in the material feed region, which is coupled with the fill level measuring device and the temperature measurement of the process temperature, a means for transporting the discharged treated material further, an exhaust gas purification system comprising at least one fine filter for separating off dust-like material and discharging it into the product stream, a plurality of scrubbing stages for desulfurizing the exhaust gas stream, for example a scrubbing stage using water and two scrubbing stages using milk of lime, at least one explosion flap in the exhaust gas system to protect against overpressure, and a heat exchanger for cooling the exhaust air in the exhaust gas stream and for simultaneously preheating the process air.

16. Process according to claim 1 wherein preheated process air is introduced into the fluidized bed furnace.

17. Process according to claim 1 wherein the fluidized bed furnace is operated at a pressure in the range of -0.2 mbar to -0.3 mbar.

18. The apparatus according to claim 10 having two gas burners.

19. The apparatus according to claim 10 having three gas burners.

20. The apparatus according to claim 10 having a plurality of temperature sensors and at least two of the temperature sensors being vertically spaced from one another.

Description

THE DRAWINGS SHOW

[0078] FIG. 1 a process diagram to illustrate the start-up phase I;

[0079] FIG. 2 a process diagram to illustrate the continuous, autothermal phase II;

[0080] FIG. 3 a longitudinal section through the fluidized-bed furnace according to the invention;

[0081] FIG. 4 a cross section through the reactor to depict the arrangement of the burners;

[0082] FIG. 5 a cross section through the reactor to depict an alternative configuration of the arrangement of the burners.

[0083] FIG. 1 shows a process flow diagram to illustrate the phase I of start-up of the fluidized-bed furnace according to the invention. The start-up phase of the fluidized-bed furnace can be described as follows:

[0084] 100 For start-up, the fluidized-bed furnace is firstly filled with about 1.5 t of previously reprocessed material which no longer contains, in particular, any oil residues and sulfur residues. If exclusively untreated waste materials were utilized for first-time filling of the fluidized-bed furnace in the start-up phase, this could lead to conglutination of the materials and to subsequent sintering when heat is applied. This would have an adverse effect on the start-up process. The initial filling with previously reprocessed waste materials is also important because not too much fuel may be present in the fluidized-bed furnace during one-off ignition of the process, which would lead to uncontrolled evolution of heat.

[0085] 110 At the same time as step 100, heating of the fluidized-bed furnace, in particular of the previously treated waste materials which have been introduced into the fluidized-bed furnace, occurs. Heating is preferably effected using at least one, preferably two, particularly preferably three, gas burner(s) on the basis of natural gas.

[0086] 120 To start the fluidization of the material in the fluidized-bed furnace, the blowing of process air, which has preferably been preheated to from 45 to 130° C., into the fluidized-bed furnace is commenced simultaneously with commencement of the introduction of the previously treated waste materials in step 100. The process air is preferably blown into the fluidized-bed furnace from below.

[0087] 130 The introduction of “untreated” waste materials containing valuable metals is then commenced.

[0088] 140 After commencement of the introduction of the untreated waste materials containing valuable metals, the reaction, i.e. the burning-off of the oil and sulfur residues, is then ignited once using a separate burner, the ignition burner.

[0089] 150 When the process temperature (from 630° C. to 730° C.) has been reached, all burners, including the ignition burner, are switched off and the process goes over into phase II, i.e. the process from then proceeds continuously and autothermally 200.

[0090] 160 After successful conclusion of the start-up phase I, the ignition burner is taken out of the process. The process from then proceeds continuously and autothermally 200 over many months up to a number of years. The process has to be interrupted only when maintenance or repair is necessary on the fluidized-bed furnace because of material wear. Maintenance which can be carried out within 2 to 3 days does not require a renewed start-up phase I; although the process temperature in the bed of the material does drop over this period of time, it is always still sufficiently high for continuation of the continuous phase II. After conclusion of any such brief maintenance or repair, the continuous and autothermal operation of the fluidized-bed furnace can therefore be continued directly.

[0091] FIG. 2 shows a flow diagram to illustrate the continuous, autothermal phase II 200 for recycling of waste materials containing valuable metals in the fluidized-bed furnace of the invention. The continuous, autothermal phase II 200 can be described as follows:

[0092] 200 denotes the continuous, autothermal phase II in the fluidized-bed furnace. The special aspect of phase II is that no more heat apart from the preheating of the process air has to be introduced into the fluidized-bed furnace after the one-off ignition. A sufficient amount of sulfur and carbon compounds adhere to the waste materials containing valuable metals for there to be sufficient fuel in the system to keep the process temperature in the range from 630° C. to 730° C.

[0093] In this example, catalyst materials from the petroleum industry were used as waste materials containing valuable metals. These contained about 80% of aluminium oxide, about 12% of molybdenum and about 8% of nickel and/or cobalt. The catalyst batches also contained three particle size fractions: dust, larger fragments and a fraction comprising intact catalyst particles. Main impurities after use of the catalyst batches in petroleum refining processes are oil residues and sulfur.

[0094] The continuous, autothermal phase II in the fluidized-bed furnace is characterized by the following process parameters: [0095] Reactor temperature: 630° C.-730° C. [0096] Process air: 45-130° C., 3000 to 5000 kg/h [0097] Flow rate of material through the furnace: about 1000 kg/h [0098] Residence time of the material: about 4 h [0099] Fill level of the reactor: 15% to 25% [0100] Pressure in the reactor: -0.2 to -0.3 mbar

[0101] 210 symbolizes the introduction of waste materials containing valuable metals, which takes place in the upper part of the fluidized-bed furnace. The process temperature is kept in the preferred range from 630° C. to 730° C. during the continuous, autothermal phase II, preferably in a simple way via control of the flow rate of material through the furnace. The flow rate of waste materials containing valuable metals which are to be treated is in the range from 800 to 1200 kg/h, preferably from 900 to 1100 kg/h, particularly preferably about 1000 kg/h. To control the inflow rate of material, the fluidized-bed furnace is preceded by a differential metering balance. The amount of material introduced is regulated by means of an SPS which controls the differential metering balance, with back-coupling being effected with the process temperature in the fluidized-bed furnace and the fill level measuring device of the fluidized-bed furnace.

[0102] If the temperature in the bed of material drops below the intended range, the inflow rate of material is increased. Conversely, the inflow rate of material is decreased when the temperature in the bed of material rises above the intended range.

[0103] 220 The discharge of the treated material occurs at the lower end of the fluidized-bed furnace under gravity by means of a discharge apparatus which contains controllable flaps.

[0104] 230, 240 After exit from the fluidized-bed furnace, the treated material can be processed further depending on customer wishes, for example in a rotary tube furnace 230. The material which has been treated further in this way is then packed 240 for delivery to customers.

[0105] 250 However, the material is usually discharged into a stock vessel from where it is transported away via transport devices, for example a cooling transport screw and pneumatic transport devices, to a packaging facility for Big Bags.

[0106] 260 symbolizes dispensing into Big Bags.

[0107] 300 symbolizes the introduction of process air. To burn off organic residues such as oil residues and carbon deposits which adhere to the waste materials containing valuable metals, the fluidized-bed furnace is supplied with from about 3000 to 5000 kg/h of process air in the continuous, autothermal phase II. This amount of air has been found to be sufficient to burn off oil residues and the carbon deposits efficiently and essentially completely from the waste materials containing valuable metals. The process air is ideally preheated to a temperature in the range from 45° C. to 130° C. before introduction into the fluidized-bed furnace. This process air is preheated atmospheric air. To preheat the process air, it is possible to utilize, for example, the waste heat of the fluidized-bed furnace, i.e. the heat of the filtered combustion air 310, with preheating being carried out in a heat exchanger 340. The heat exchange for preheating the process air 300 is symbolized by the dotted arrows between 300 and 340. Hot steam 350 is used for preheating the process air 300. The hot steam 350 is produced by heating water by means of the filtered exhaust air described in the following stage 310.

[0108] 310 Exhaust gases which contain, inter alia, dust-like material, which owing to the mode of operation is discharged from the fluidized-bed furnace, and sulfur, mainly in the form of sulfur oxides such as SO.sub.2 and SO.sub.3, arise in the process of the invention. For reasons of environmental protection, the emission of these materials into the environment should be avoided if possible. 310 symbolizes the first step of exhaust gas purification. To remove the dust-like materials from the exhaust gas stream, the exhaust gas stream is filtered. Filtering of the exhaust gases is carried out using commercial filters, preferably using coarse filters and fine filters. Suitable coarse and fine filters consist, for example, of stainless steel. The process of the invention is particularly environmentally friendly since the dust-like materials which are removed from the exhaust gas stream by means of the coarse and fine filters are directly added to the treated product (symbolized by the broken line between 310 and 250 or between 310 and 230).

[0109] 320 To remove the sulfur, i.e. the sulfur oxides, the exhaust gas stream is scrubbed. Scrubbing of the exhaust gas stream generally comprises a plurality of scrubbing stages, with scrubbing being carried out using water and milk of lime. The scrubbing with water serves to remove residual portions of dust in the exhaust gas stream. Scrubbing with milk of lime serves to separate sulfur oxides from the exhaust gas stream, with the sulfur oxides being reacted with the milk of lime to form gypsum. To assist the removal of the sulfur oxides, an additional scrub of the exhaust gas stream using sodium hydroxide solution can be carried out in a further scrubbing stage.

[0110] 330 symbolizes the purified and cooled combustion air which is discharged into the atmosphere.

[0111] 350 symbolizes hot steam which is produced by heating water by means of the filtered exhaust air described in step 310. The hot steam is utilized in the process of the invention in order to preheat the process air 300 in the heat exchanger 340.

[0112] FIG. 3A shows a schematic depiction of the fluidized-bed furnace 100 of the apparatus of the invention. The fluidized-bed furnace 100 comprises a steel vessel 108 having a refractory lining 118. Introduction of the waste materials containing valuable metals during the continuous, autothermal phase II is carried out via the material inlet 101. In the start-up phase I, prefilling with previously treated material is also carried out via the material inlet 101. The discharge of the treated material is effected at the lower end of the steel vessel 108 under gravity via the material outlets 110 and 111. Discharge apparatuses with integrated flaps for controlling the rate of discharge of material can be arranged at the material outlets 110 and 111.

[0113] The introduction of the process air 102, which has preferably been preheated, is effected at the lower end of the steel vessel 108. To obtain better distribution of the process air and optimal fluidization of the waste materials containing valuable metals, the process air is blown into the steel vessel 108 via an air distributor 104 having a plurality of air nozzles 105. The outlet 103 for the exhaust gases or the combustion air is located at the upper end of the steel vessel 108.

[0114] The rate of introduction of the waste materials containing valuable metals and the rate of discharge of material are controlled with the aid of a fill level measuring device in the fluidized-bed furnace 100. For this purpose, the fluidized-bed furnace comprises a fill level measuring device which operates reliably at the high process temperatures in the range from 630° C. to 730° C. and the reduced pressure in the range from -0.2 to -0.3 mbar prevailing in the steel vessel. The fill level measuring device operates on the basis of a differential pressure measurement between two measurement points 112, 113, of which one measurement point, i.e. a first pressure sensor 113, is arranged above the bed of material in the steel vessel 108 of the fluidized-bed furnace 100 and one measurement point, i.e. a second pressure sensor 112, is arranged below this bed of material. To increase the reliability and measurement certainty, this differential pressure measurement is configured redundantly. The fill level measuring device is configured so that the fill level in the steel vessel is calculated with the aid of the differential pressure measurement, but preferably taking into account the temperature prevailing in the steel vessel and the pressure prevailing in the steel vessel. The fill level in the steel vessel 108 is kept in the range from 15% to 25%, preferably from 16% to 21%.

[0115] The process temperature is kept in the range from 630° C. to 730° C. in the bed of material. For reliable temperature monitoring, the fluidized-bed furnace 100 therefore has at least one temperature sensor, preferably a plurality of temperature sensors, particularly preferably six temperature sensors 114, 115 and 116, with at least two measurement points preferably being distributed vertically over the bed of material. In addition, the fluidized-bed furnace 100 can have further temperature sensors, for example the temperature sensor 117, which measure the temperature above the bed of material within the steel vessel 108.

[0116] The fluidized-bed furnace 100 is operated under reduced pressure, preferably at a pressure in the range from -0.2 to -0.3 mbar, during the continuous, autothermal phase II. To measure the pressure, at least one pressure meter 119 is present in the interior of the fluidized-bed furnace. The reduced pressure in the interior of the fluidized-bed furnace in the range from -0.2 to -0.3 mbar is generated and regulated by, inter alia, extraction of the exhaust gases via the outlet 103.

[0117] During the start-up phase I, the fluidized-bed furnace 100 is heated by the three burners 106A, 106B and 106C until the operating temperature in the range from 630° C. to 730° C. has been reached in the steel vessel 108. It can be seen in FIG. 3A that the three burners are arranged via the inlets 106A, 106B and 106C in the upper third of the steel vessel 108. The inlet tubes of the three burners 106A, 106B and 106C are, in the embodiment shown here, arranged so that the air inflow stream is at an angle of 45° relative to the wall of the steel vessel 108. Other possible ways of arranging the inlet tubes are likewise conceivable.

[0118] The apparatus of the invention can contain, in addition to the fluidized-bed furnace 100, one or more auxiliary and additional devices selected from among [0119] a differential metering balance in the material feed region (coupled with the fill level measuring device and the temperature measurement of the process temperature), [0120] a means for transporting the discharged treated material further, for example comprising a cooling transport screw, a pneumatic transport device and a packaging device for Big Bags, [0121] optionally a rotary tube furnace for calcining and/or further processing the product, [0122] an exhaust gas purification system, for example comprising [0123] at least one coarse filter and at least one fine filter for separating off dust-like material and discharging it into the product stream, [0124] a plurality of scrubbing stages for desulfurizing (to form gypsum) the exhaust gas stream, for example a scrubbing stage using water and two scrubbing stages using milk of lime, [0125] optionally an additional stage for scrubbing the exhaust gas stream with dilute sodium hydroxide solution, [0126] one or more explosion flaps in the exhaust gas system to protect against overpressure, [0127] a heat exchanger for cooling the exhaust air in the exhaust gas stream, with the waste heat being utilized for preheating the process air.

[0128] Furthermore, the apparatus of the invention comprises a control device for controlling the fluidized-bed furnace 100 during the continuous, autothermal phase II, which is configured for [0129] controlling the fill level measuring device so that the fill level of the steel vessel 108 is kept in the range from about 15% to 25%, preferably from 16% to 21%, by means of the differential pressure measurement 112, 113 and taking into account the high process temperatures of from 630° C. to 730° C., with the discharge of material being effected under gravity by control of the flap in the material outlets 110 and 111; [0130] and/or keeping the process temperature in the range from 630° C. to 730° C., with the process air being preheated to a temperature in the range of 45° C. - 130° C. by means of the heat exchanger, [0131] and/or setting the pressure in the interior of the steel vessel 108 of the fluidized-bed furnace 100 in the range from -0.2 to -0.3 mbar.

[0132] The fluidized-bed furnace 100 according to the invention can further comprise reserve ports 120, 121, 122 and also a sight glass 123 with flushing connection for visual process monitoring.

[0133] FIG. 3B shows a section of the wall of the fluidized-bed furnace 100 with the steel vessel 108 which has the connection 109 of the ignition burner for starting up the fluidized-bed furnace in phase I. The ignition burner is taken from the process after successful conclusion of the start-up phase I.

[0134] FIG. 3C shows a section of the wall of the fluidized-bed furnace 100 with the steel vessel 108, which has the lower pressure sensor 112 and the upper pressure sensor 113 for the differential pressure measurement as a basis for the fill level measuring device of the apparatus of the invention.

[0135] FIG. 4 shows a cross section through the fluidized-bed furnace 100 with the three burners 106A, 106B and 106C which are operated using natural gas for heating the steel vessel 108 during the start-up phase I until the process temperature in the range from 630° C. to 730° C. has been attained. The three burners 106A, 106B and 106C are arranged at a spacing of in each case 120° around the circumference of the steel vessel 108. The burner inlets 106A, 106B and 106C contain steel tubes which are surrounded by a refractory coating 118.

[0136] FIG. 5 shows a cross section through the fluidized-bed furnace 100 with the three burner inlets 106A, 106B and 106C which are operated using natural gas for heating the steel vessel 108 during the start-up phase I until the process temperature in the range from 630° C. to 730° C. has been attained. The three burner inlets 106A, 106B and 106C are arranged at a spacing of in each case 120° around the circumference of the steel vessel 108. In the embodiment shown here, the burner inlets 106A, 106B and 106C consist entirely of refractory materials 118 and do not contain any steel tubes.

TABLE-US-00001 List of reference numerals 100 Fluidized-bed furnace 101 Inlet for introduction of material 102 Inlet for process air 103 Outlet for exhaust air 104 Air distributor 105 Air nozzles 106A, B, C Burners 107A, B, C Sight glass for burner 108 Steel vessel 109 Ignition burner connection 110, 111 Outlet for material 112 Lower pressure meter for fill level measuring device 113 Upper pressure meter for fill level measuring device 114, 115, 116 Temperature meter in the bed of material 117 Temperature meter above the bed of material 118 Refractory lining or coating 119 Pressure sensor 120, 121, 122 Reserve ports 123 Sight glass with flushing connection